The present invention relates to a cylinder head gasket with an auxiliary sealing plate around cylinder bores for securely sealing therearound.
An automobile engine has been developed to provide high power with light weight. In order to satisfy this demand, an aluminum alloy has been used for a cylinder block as well as a cylinder head. Also, the distance between the cylinder bores is set as short as possible, and combustion pressure is increased.
Under the circumstances, high temperature and high pressure are applied to the cylinder head, especially to portions between the cylinder bores. These high pressure and high temperature are also applied to a gasket situated between the cylinder head and the cylinder block.
A gasket is provided with sealing means, such as a bead, a grommet and the like, for sealing around the cylinder bores. When the gasket is tightened, the sealing means is compressed to provide surface pressure thereat, by which areas around the cylinder bores are sealed.
In case a gasket is formed of a flexible material, such as a mixture of carbon or inorganic fibers and binders, such a flexible material is not strong against high temperature. In case a gasket is a steel laminate gasket formed of a plurality of steel plates, although the steel laminate gasket is generally strong against high temperature and high pressure, if extremely high temperature and high pressure are applied to the steel laminate gasket or the gasket is used for a long period of time, creep relaxation may occur. Also, decrease of surface pressure is liable to occur at the areas between the cylinder bores, to which high temperature and high pressure are applied.
Namely, in a conventional gasket, in case high temperature and high pressure are applied at the areas between the cylinder bores, leakage may happen around the cylinder bores.
In order to provide high surface pressure at a specific area, a surface pressure regulation plate may be installed on a gasket, as disclosed in U.S. Pat. No. 4,776,073. However, even if the conventional surface pressure regulation plate is used, the desired local surface pressure may not be obtained. Also, since the conventional surface pressure regulation plate is made separately, it is troublesome to provide a plurality of the conventional surface pressure regulation plates in one gasket.
In French Patent No. 2,521,638, a gasket is formed of a plurality of metal plates, wherein some plates extend partly around areas to be sealed. However, it does not locally provide high surface pressure.
Accordingly, one object of the present invention is to provide a cylinder head gasket for securely sealing around the cylinder bores.
Another object of the invention is to provide a cylinder head gasket as stated above, wherein high surface pressure is locally formed at an area between the cylinder bores situated adjacent to each other.
A further object of the invention is to provide a cylinder head gasket as stated above, which can be easily and economically manufactured.
Further objects and advantages of the invention will be apparent from the following description of the invention.